1. Technical Field
This invention generally relates to mining exploration equipment and methods. In particular it relates to an apparatus and method, to be used infield for preparing ore samples and recovering water for reuse.
2. Background Art
Current day practice in mineral exploration uses truck mounted reverse flow or dual tube drilling rigs to extract subsurface samples for mineral content analysis. The reverse flow drilling process requires that drilling fluid be pumped down the outer tube of the drill and returned to the surface, along with the drill cuttings, up through the inner tube. In the early stages of drilling, compressed air is used as the fluid. As soon as the cuttings become moist, water is pumped down the drill shaft, and the cuttings are brought up in a slurry. For this reason, a tanker truck always follows the drilling rig to supply the necessary water. Once the drill has consumed all of the water in the tanker truck, drilling must be either slowed or stopped until the tanker truck is able to locate a water source and refill. For a typical fourteen hour drilling day, this translates into about two hours of down time waiting for water. This is obviously a significant problem.
There are also environmental concerns associated with the tanker trucks combing the countryside to refill out of a local stream or pond, providing they can even locate a water source. In some cases, the water shortage problem is so bad that drillers have resorted to flying water into remote locations with helicopters. This is very expensive and inconvenient.
Once the cuttings have been brought to the surface, they are examined and logged by geologists to determine their mineral content. The cuttings are brought to the surface in large amounts of slurry. Consequently, in order for the geologist to examine the fine cuttings, he or she must retain and dry large quantities of the slurry. This is typically accomplished by applying samples to drying boards and allowing the water to evaporate off. The samples on the drying boards must also be catalogued in chronological order to maintain the integrity of the analysis.
LUMMUS, ET AL., U.S. Pat. No. 3,016,962, teaches a partial solution to this problem. Lummus uses a process and apparatus in which the slurry from the drilling well is introduced directly into a hydrocyclone. The hydrocyclone separates the drilling fluid from the cuttings and directs the fluid to a storage tank so that it can then be reused in the drilling process. Lummus does not teach, nor make any special provisions for, maintaining the integrity of the cutting sample. Lummus' sole concern is with water recovery. Also, the bit cuttings introduced into the hydrocyclone cannot exceed a maximum size as this results in clogging of the hydrocyclone apex. Additionally, particles below a particular minimum size are rejected in the recovered water stream and sent back down the drill or settled out in the storage tank. This particular method and apparatus produces an unacceptable ore sample for the geologist. In order to make a valid assessment of the sample, the sample must contain both large and small particles. Additionally, the samples must be taken in a batch manner to insure the integrity of any stratification layer analysis.
In the past, mining companies have made the decision not to mine a specific site based upon the erroneous finding that there was insufficient mineral content in the drilling samples. The erroneous findings result from the rejection of the fine particles contained in the recovered water and/or discarded drilling mud. It only takes 0.03 ounces of gold per ton of ore to justify mining a particular site. It is easy to see how present day drilling methods and those shown in the prior art result in a significant amount of the mineral going undetected.
Using the method taught by Lummus, the intermediate particles filtered out by the hydrocyclone are separated from any small particles, either settling out in the storage tank or being reinjected down the drilling shaft, along with the larger prescreened particles, which have to be removed from the drilling fluid before it is introduced into the hydrocyclone to prevent clogging of the apex. The end result is that the geologist is presented with three separate samples with little or no chronological correlation, including an incomplete small particle sample.
What is needed is an apparatus and method for batch ore sampling and water recovery which can be used in the field by the drilling rig operator and easily transported from one drilling site to another. It is therefore an object of the present invention to provide such a method and apparatus.